The YouTube video above includes an interview with Deborah Shelton from 1987 [Thanks to Alex for finding it!]. At about the 5:40 mark, the interviewer asks her about Body Double. Here is a transcript:

Interviewer: In 1984, you ended up in the Brian De Palma movie, Body Double. How did that happen?

Deborah: Same way—I went on an interview and they were looking for a blonde. [Laughing] There’s something about... Yeah, I have a blonde personality. And I met him, and he was very quiet. And the executive producer was talking to me all the time, and the casting person. And Brian just sat there and was like [lifts her chin up to mimic De Palma, slowly nodding as if quietly watching and contemplating what he was seeing]. And sometimes he looked away, and he didn’t… I thought, “Oh, get me out of here. This is a lost cause.” And when I left there I stopped off at the bathroom on the way out of the building. And when I finally got out of the building, the lady who was the casting director was running around hysterically outside searching for me. And she said, “Where were you?” Then I told her I’d just stopped off. And she said, “Brian wants to see you tomorrow at his office, and he wants to work with you.”

And he worked with me, with the screenplay… oh, I can’t think, with Liv Ullmann… Scenes From A Marriage, on a scene where she had just learned her husband was fooling around for a long time, and that her best friends had known it. She was very angry and frustrated. And another scene from Body Heat… where the two meet on a bridge. And so, he told me he wanted the sensuality of Body Heat, and the frustration and panic, and those kind of feelings from Scenes From A Marriage. So we worked on those two scenes, and those are the ones I did with my screen test. Because my part didn’t really have so much dialogue. And I got it.

And how was he as a director? I mean, on the set…

Wonderful.

Really?

He’s very intense. He almost has an unnerving way about him. And you know Vincent Price? The actor? He has a way of looking, the piercing eyes, that just kind of go into your backbone, and take feelings out of you. And I think that’s the way Brian is.